1. Field of the Invention
The present invention relates to a fluid operated, brake device for use in a vehicle having a valve device for facilitating initial backward movement of the vehicle from a halt on an upward slope, and more particularly, to a brake device provided with a brake actuating mechanism which is operated during backward moving of a vehicle on an upward slope.
2. Description of the Prior Art
As a prior art fluid operated brake device for facilitating the starting operation for re-starting a vehicle after a stop on an upward slope, there is known a device disclosed in Japanese Published Application No. Sho 56-34550. In this device, the braking action is maintained by containment of the brake fluid pressure when a clutch pedal is depressed to allow a clutch to be uncoupled, and the braking action is released when the clutch pedal is returned.
Accordingly, by using the prior art brake device stated above, the starting operation on an upward slope will be facilitated since a returning action of the clutch pedal is effected after the acceleration pedal is depressed to an optimum position.
On the contrary, in the other brake device in which the brake fluid is released only by depressing an acceleration pedal, this release operation occurs whenever the acceleration pedal is depressed until the same position. Accordingly, an engine torque in such case is always constant, resulting in that the engine torque is too small or too large with respect to a predetermined engine torque appropriate for the inclination of a upward slope.
As stated above, since the prior art brake device is designed so as to release the brake fluid in response to the returning operation of a clutch pedal, a starting operation during starting of a vehicle on an upward slope becomes easy. However, it is likely that the following inconvenience occurs during backward starting.
Namely, when a vehicle is stopped at a desired position by backwardly moving the vehicle, it is often executed by simultaneously depressing a brake pedal and the clutch pedal. In this condition in which the vehicle is placed in a decelerated condition, a valve, element such as a ball provided within a brake retainer valve tends to move in the backward direction of the vehicle toward a valve seat by its gravity. Accordingly, during the depressing of the brake pedal if the clutch pedal is depressed, a brake fluid appearing immediately or slightly before the clutch pedal is depressed is entrapped on a wheel cylinder of a brake actuating device. As a result, even if an attempt is made to return the brake pedal from a certain depressed position for reducing a braking force, the brake fluid is still trapped so that the braking action is maintained as it is. This causes the problem that a vehicle is unable to stop at a desired position.